The present invention is directed to fiber optical transport systems. More particularly, the invention provides a method and system for reducing the size and cost of optical transmitter systems. Merely by way of example, the invention has been applied to DWDM optical transport systems. But it would be recognized that the invention has a much broader range of applicability.
Since its first deployment in the middle of 1990s, dense wavelength division multiplexing (DWDM) has become a dominant technology for long haul and regional backbone transport networks, and is gradually making its way to metro area networks. In a conventional DWDM system, each optical component, be it a laser or a MUX filter, is individually packaged. A linecard is built around one or several optical components. For example, a transmitter card for a given wavelength includes a laser and a modulator (or an integrated laser/modulator). The laser chips sitting inside the laser packages are typically made of indium phosphide (InP) semiconductor compounds. The optical outputs of multiple transmitter linecards at different wavelengths are combined through a multiplexer linecard, which includes some MUX filters. A commonly used MUX filter is based on array waveguide grating (AWG) made of silica-on-silicon. The optical connections between the linecards are through optical fibers. The optical output from the multiplexer linecard is then amplified by an optical amplifier and launched into the transmission fiber.
Even though these conventional DWDM systems are useful in some areas, they have many limitations that restrict their effectiveness in broader applications. Some of these limitations are discussed below, and then improved techniques based on embodiments of the present invention are presented.